Medicare Part D Explained
Medicare Part D helps cover outpatient prescription medications. The right plan depends on your exact prescriptions, dosages, pharmacies and eligibility—not simply which plan has the lowest monthly premium.
What Is Medicare Part D?
Medicare Part D is prescription drug coverage offered by private insurance companies approved by Medicare. It helps pay for covered brand-name and generic outpatient medications.
You can generally receive Medicare drug coverage in one of two ways:
Standalone Part D Plan
A standalone Prescription Drug Plan, commonly called a PDP, can be added to Original Medicare. People who choose Original Medicare with a Medicare Supplement commonly obtain their drug coverage this way.
Medicare Advantage With Drug Coverage
Many Medicare Advantage plans include Part D coverage in the same plan. These are often called Medicare Advantage Prescription Drug plans, or MAPD plans.
How Medicare Part D Costs Work in 2026
Every plan has its own premium, formulary, pharmacy network and cost-sharing structure. However, all Medicare Part D plans must follow federal Part D rules.
Deductible Stage
Your plan may require you to pay a deductible before it begins sharing the cost of certain medications. No Part D plan can have a deductible higher than $615 in 2026.
Some plans have a lower deductible, no deductible or apply the deductible only to certain drug tiers.
Initial Coverage Stage
After the applicable deductible, you pay the plan’s copayment or coinsurance for each covered prescription. Your cost depends on the drug tier, pharmacy, quantity and plan rules.
Catastrophic Coverage
Once your qualifying out-of-pocket spending reaches $2,100 in 2026, you pay no additional copayment or coinsurance for covered Part D drugs for the remainder of the calendar year.
Is There Still a Part D Coverage Gap?
The traditional Part D “donut hole” ended with the redesigned Part D benefit in 2025. You no longer move into a separate coverage-gap stage where your costs are calculated under the former donut-hole rules.
In 2026, Part D generally consists of a deductible stage when applicable, an initial coverage stage and catastrophic coverage after the $2,100 out-of-pocket threshold is reached.
This does not mean every prescription will be inexpensive. Your cost before reaching the threshold still depends on your plan, drug tier, pharmacy and whether the medication is covered.
What Is a Part D Formulary?
A formulary is the plan’s list of covered prescription drugs. Every Part D plan has its own formulary and usually divides covered drugs into tiers.
| Plan Feature | Why It Matters |
|---|---|
| Drug formulary | Confirms whether the plan covers your exact medication and dosage. |
| Drug tier | Helps determine the copayment or coinsurance you may pay. |
| Prior authorization | May require the plan to approve a medication before it will cover it. |
| Step therapy | May require you to try another covered medication before the plan covers the prescribed drug. |
| Quantity limits | May limit how much medication the plan covers during a particular period. |
| Preferred pharmacy | A preferred network pharmacy may charge less than a standard network pharmacy under the same plan. |
Why the Lowest-Premium Plan May Not Cost the Least
Part D plans should be compared using your entire prescription list. A plan with a very low premium could cost more overall if one of your medications is placed on a higher tier or your pharmacy is not preferred.
A useful Part D comparison should include:
- Every prescription’s exact name, dosage and frequency
- Whether each medication is included on the formulary
- The tier assigned to each medication
- Prior authorization, step therapy or quantity limits
- Your preferred local and mail-order pharmacies
- The plan’s premium and deductible
- Estimated copayments and coinsurance throughout the year
- The plan’s estimated total annual cost—not just its premium
Formularies, premiums and pharmacy pricing can change from one year to the next. Your prescriptions can also change. That is why Part D coverage should be reviewed annually rather than treated as a permanent one-time decision.
Do You Need Part D If You Take No Prescriptions?
Part D is voluntary, but going without drug coverage can create a future penalty. If you go 63 consecutive days or longer after your eligible enrollment period without Part D or other creditable prescription coverage, Medicare may add a late-enrollment penalty to your Part D premium.
The penalty is generally based on the number of complete months you went without creditable drug coverage. It can continue for as long as you have Medicare drug coverage.
If you have drug coverage through a current employer, union, VA, TRICARE or another source, do not cancel it until you understand how it coordinates with Medicare. Keep every creditable-coverage notice you receive.
Extra Help and the Medicare Prescription Payment Plan
Medicare Extra Help
Extra Help, also called the Part D Low-Income Subsidy or LIS, can help eligible Medicare beneficiaries pay Part D premiums, deductibles and prescription cost sharing.
Some people qualify automatically through Medicaid, Supplemental Security Income or a Medicare Savings Program. Other people can apply based on their income and resources.
Medicare Prescription Payment Plan
The Medicare Prescription Payment Plan allows people with Part D coverage to spread eligible out-of-pocket prescription costs across the remaining months of the calendar year instead of paying the full amount at the pharmacy.
Participation is voluntary. It changes when you pay—it does not reduce the total cost of your medications or replace your plan premium.
When Can You Join or Change Part D Coverage?
Initial Enrollment Period
When you first become eligible for Medicare, you generally have a seven-month Initial Enrollment Period surrounding your 65th birthday. Different timing can apply when Medicare eligibility begins because of disability.
Annual Enrollment Period
From October 15 through December 7, eligible beneficiaries can generally join, change or drop Medicare Advantage and Part D coverage for the following calendar year.
Special Enrollment Periods
Certain events—including losing creditable coverage, moving, qualifying for Extra Help or changes involving Medicaid—may provide another opportunity to change coverage.
Enrollment rules depend on your exact circumstances. Do not cancel existing coverage until you have verified when the replacement coverage will begin.
Medicare Part D Questions
Does Original Medicare include prescription drug coverage?
Original Medicare does not normally cover prescriptions you obtain from a retail or mail-order pharmacy. You can generally obtain this coverage through a standalone Part D plan or a Medicare Advantage plan that includes prescription coverage.
Can I have a Medicare Supplement and Part D?
Yes. Medicare Supplements generally do not include outpatient prescription coverage, so people with Original Medicare and Medigap commonly enroll in a separate Part D plan.
Can I have Medicare Advantage and a separate Part D plan?
Usually not. Most people who want Medicare Advantage prescription coverage must choose a Medicare Advantage plan that includes Part D. Joining a standalone Part D plan while enrolled in certain Medicare Advantage plans can cause disenrollment from the Medicare Advantage plan.
Ask for individualized guidance before attempting to combine these types of coverage.
Does every Part D plan cover the same medications?
No. Each plan has its own formulary, tiers and coverage restrictions. Medicare establishes certain coverage requirements, but plans can differ significantly in how they cover a particular prescription.
Does the $2,100 limit include my Part D premium?
No. The 2026 threshold applies to qualifying out-of-pocket spending for covered Part D medications. Monthly premiums do not count toward that threshold.
What happens if my medication is not on the formulary?
You may be able to ask the plan for a formulary exception or coverage determination with support from your prescriber. You may also need to consider an alternative covered medication. Approval is not automatic.
Should I review my Part D plan every year?
Yes. Plans can change premiums, formularies, drug tiers, pharmacy relationships and coverage restrictions. Reviewing the plan using your current medications and pharmacies can help identify changes before the next coverage year.
Let’s Review Your Prescriptions and Pharmacies
Benjamin Thompson can help you compare available Medicare Part D and Medicare Advantage prescription coverage using your actual medications, dosages and preferred pharmacies. You will receive a clear explanation without high-pressure sales.
Thompson Medicare Brokerage serves Medicare beneficiaries throughout Missouri and Illinois, including Springfield, Bucyrus, Houston and the surrounding Texas County communities.
This page provides general educational information and is not a substitute for guidance from Medicare, Social Security, an employer benefits administrator, your prescribing physician or another appropriate agency regarding your individual circumstances. Plan availability, formularies, pharmacies, costs and coverage rules vary by plan, location and coverage year.